1. Field of the Invention
This invention is directed to composite polymer electrolytes for alkali metal or alkali metalxe2x80x94ion based electrochemical devices that contain electrically non-conductive fibers, which have been chopped into short lengths and mixed with other components to form the electrolytes.
2. Description of the Prior Art
Electrochemical devices such as batteries of the solid state type consist of at least an anode, a layer of electrolyte, and a cathode. A variety of compositions have been proposed for polymer electrolytes which have advantages and disadvantages. It is desirable to have electrolytes which are strong, with mechanical resistance against compression and shorting. The electrolytes contain additions to meet the described requirements such as powdered electrically non-conductive particles, mats, or woven or non woven fabric, as described in prior U.S. patent application Ser. No. 09/006,057, filed Jan. 12, 1999.
Examples of other prior art structures are shown and described in the U.S. Patents to Balanger, No. 3,485,677; Rippel, et al., No. 4,275,130; Basu, No. 4,304,825; Bannister, No. 4,471,370; Suguichi, et al., No. 4,496,638; Murray, No. 4,497,883; Skotheim, No. 4,529,086; Hope, et al., No. 5,102,752; Kejha, et al. No. 5,521,023; and Kejha No. 5,705,084.
While the described composite electrolytes are satisfactory for some uses, they may be subject to problems, such as delamination, or excess weight, or cost, or high resistance, or incompatibility with other components. The composite electrolytes of the invention do not suffer from these problems and provide many advantages.
It has now been found that composite polymer electrolytes that contain electrically non-conductive chopped fibers for use in alkali metal based electrochemical devices, such as batteries, capacitors and sensors, provide a strong lightweight composite structure, with a long shelf and operating life, with increased mechanical resistance to compression and shorting, and which are suitable for mass production, providing a rugged device with improved yield.
The principal object of the invention is to provide composite polymer electrolytes for alkali metal based electrochemical devices which contain electrically non-conductive chopped fibers, with improved mechanical resistance to compression and shorting.
A further object of the invention is to provide composite polymer electrolytes for alkali metal based electrochemical devices, which are useful with a wide variety of devices.
A further object of the invention is to provide composite polymer electrolytes for alkali metal based electrochemical devices, which electrolytes can be formed separately, or coated directly onto an electrode.
A further object of the invention is to provide composite polymer electrolytes for alkali metal based electrochemical devices that have high ionic conductivity and lend themselves to economical mass production.